Method of waterproofing leather



-.without discoloring or darkening the leather.

United States Patent O 3,052,571 METHOD OF WATERPROOFING LEATHER CharlesA. Fetscher, Short Hills, and Stanley Lipowski, Newark, N. J., assignorsto Nopco Chemical Company, Harrison, NJ., a corporation of New Jersey NoDrawing. Filed July 11, 1958, Ser. No. 747,818 9 Claims. (Cl. 117-142)This invention relates to a new and improved process for thewaterproofing of leather. More particularly, the invention relates to awaterproofing process which is especially well suited for use inconnection with the waterproofing of white leathers.

For obvious reasons, waterproofing is an extremely important step in thefinishing of leather. However, it is of equal importance that thewaterproofing of leather be accomplished without adversely aifecting theair permeability or water-vapor permeability of the leather and Manymethods have been disclosed in the prior art as being .suitable for usein rendering leather waterproof. Some of these havebeen moresatisfactory than others. In most cases the proposed methods have beensuccessful in providing the leather with the. desired resistance topenetration by water or moisture. 'In many instances, however, this hasbeen accomplished only-by sacrificing the permeability of the leather toair and water-vapor. In other instances, the desired waterproofing hasbeen achieved but with a leather.

In all probability the most well known of the prior art leatherwaterproofing processes involves the drumming of emulsions of a wax orgrease into the tanned skin prior to drying same. More recently,improved methods for the waterproofing of leather have been devised.These involve, for example, the treatment of leather with oil-in-wateremulsions of various water-insoluble organic polymers.

In addition to the aforementioned methods, other waterproofing processeshave been disclosed in the art. Thus, 40

for example, it is well known that penetration of waterproofingcompounds into leather is facilitated when such compounds are added tothe leather in the form of an organic solvent solution thereof. Whensuch solutions are used, the waterproofing compounds appear to coat thesurface of the fibers. The provision of such a coating is to becontrasted with the result obtained by certain of the previous mentionedmethods wherein the waterproofing agent appears merely to be depositedin the spaces between the fibers. I

A fiow sheet representing in a schematic fashion the process of theinvention is as follows:

discoloring or darkening of the' 3,052,571 Patented Sept. 4, I962 iceThe object of invention is to provide a new and improved process for thewaterproofing of leather.

A more particular object of the invention is to provide 7 will in partappear hereinafter.

It has been discovered that the objects of this invention can beaccomplished :by treating leather which has been saturated thoroughlywith an organic solvent solution of aluminum isopropoxide with anorganic solvent solution of a soap-forming acid and subsequently washingand drying same.

The present invention contemplates the use and the treatment of tannedleather in ai-rdried condition. Preferably, our waterproofing process iscarried out on the air-dried leather immediately after the fat-liquoringstep. If desired, however, leather can be waterproofed by our methodeither prior to the fat-liquoring step or at any finishing stepsubsequent to fat-liquoring.

Furthermore, the process of the invention is such that it can beutilized in the treatment of leathers, without regard to the manner inwhich the leather has been tanned. Thus, for example, the invention canbe practiced on leathers which have been subjected to chrome tannage,alum tannage, vegetable tannage, tannage and synthetic tannages, as wellas on leathers which have been retanned.

-The process of the invention can be adapted readily for commercial use.This will be readily apparent from the description which followshereinafter. -In carrying out the process, a dilute-organic solventsolution of aluminum isopropoxide is first prepared. In general, anyorganic solvent in which aluminum isopropoxide is soluble can be used inthe preparation of this solution. In the preferred embodiment of theinvention, however, are rna-tic hydrocarbon solvents, such as, benzene,toluene, xylene, etc. are employed. The concentration of the solutionused may be varied over a relatively wide range. Preferably, a solutioncontaining from about 3.0% to about 10.0% by weight of aluminumisopropoxide will be employed. It should be understood, however, thatmore dilute or more concentrated solutions can be employed in carryingout the process, if desired. However, it has been our experience, thatby far the most satisfactory results are obtained when a solutioncontaining not less than 3.0%, by weight, or more than 10.0%,. byweight,

of aluminum isopropoxide is used.

In the first step of the preferred procedure, the tanned leather isthoroughly impregnated or saturated with the organic solvent solution ofaluminum isopropoxide thus prepared. In general, this can beaccomplished in any convenient manner. For all practical purposes,however,

the complete saturation of the leather with the solution can be broughtabout most etiiciently by totally immersing the leather in the solutionin a suitable vessel containing the solution, as, for example, in a drumor vat.

The step of saturating the leather with the solvent solution of aluminumisopropoxide can be, and is preferably, carried out at a temperaturewhich is at or near ordinary room temperatures. However, the solventsolution can be heated to a temperature which is elevated somewhat aboveroom temperatures, if .desired, prior to impregnating it into theleather which is to be waterproofed. It has been found that the use of aheated solvent solution during the step will facilitate, to some extent,the penetration of the aluminum isopropoxide solution into the leather.This means that, in such instances, complete saturation of the leatherwith the so lution can be accomplished in a shorter period of time.However, since even at room temperatures adequate sata ration can beachieved by immersing the leather in xylene, etc., are used mthe secondand third steps. 1e solution for as short a period as fifteen minutes,from In the second step, solutions contammgfrom about 3.0% n economicalstandpoint there is no real advanta e in to 10.0% by weight the soapforrmng fatty acid are sing a heated solvent solution. In any event,seldom, preferably employed; However, more d lute or more 5 ever, willit serve any useful purpose to immerse the 5 concentrated solutions canbe used, if desired. No par- :ather in a solution which has been heatedto a temperat cular advantage -is ga ned, ow by t euse Of a so- 1reabove about 50 C. lution which contains less than 3.0% weight or moreThe exact volume of the aluminunuisopropoxide soluthan 10.0% by weightof the soap-forming fatty acid. on which is employed in the practice ofour invention is The precise volume of the fatty acid solutionused otparticularly critical. When the aluminum isopropoxm the practice of theinvention is not particularly crmcal. le is introduced into the leatherby an immersion proc- For maximum effectiveness, however, a suffcientquantity ss,.,the. bath used, however, should contain a quantity offatty acid must be provided to react with all of the i fisopropoxidewhich is suflicient to impregaluminum isopropoxide presentin the interstices of ate all of the interstices of the leather.Obviously, volthe leather. The use of a solvent solution containing meof the solution which must be used in any par-ticufrom about 3.0% to10.0% by weight of fatty acid in uinstance will depend, at least inpart, on the concena sufficiently large volume to permit the completeimration of the solution. A lesser voluine of a more highly mersiontherein of the leather to be treated will provide oncentrated solutionand a greater volume of a more the system with a quantity of fatty acidwhich is more ilu-te solution will be needed to supply a sufficientquanthan enough for our purposes. The use, or presence, ity ofimpregnant. As algenera-l rule, it has been found of an excess of acidsin the bath is not economically hat the use of a solution containingfrom 3.0% to 10.0% disadvantageous since the bath can be used over and yweight of aluminum isopropoxide, in a sufficiently over again insubsequent runs, preferably after it has arge volume to permit thecomplete immersion therein been replenished by the addition of aquantity of fatty f the leather to be waterproofed, will insure thepresence acid suflicient to return it to its original concentration. aquantity of aluminum isopropoxide which is more The treatment of thealuminum isopropoxide-saturated han enough for P p It may he noted inthis leather with the solution of the soap-forming fatty acid egard thatthe use of a solution containing a greater can be, and is preferably,carried out at temperatures uantity of aluminum isopropoxide than isactually neceswhich are at or near ordinary room temperatures. Solarydoes not render the process n mi lly dlsadvanvent solutions of the fattyacid heated to temperatures ngeons- After the saEul'ated leather hasbeen Withdrawn of up to about 50 C. can be used, however, if desired.1'011 the bath, one'ean determine, y analytical methods, It has beenobserved that, when a heated solution of he q y of aluminum P Premaining in the fatty acid is used, the rate of ,the reaction of thefatty rath. The nused aluminum QP P Solution can acid with the aluminumisopropoxide is accelerated to veusedd e again, in q n ,P ?h Y someextent. Thus, for example, using an unheated tfter it has been repl ni ythe addl-hon of a q ny solvent solution, the reaction will proceed tosubstantial f aluminum iSQPYOXide Sufheient to restore it to its 8-completion when the saturated leather is allowed to stand nalconcentration. in contact with the fatty acid solution for a period ofIn t Second P of the P Procedure, h a111- about fifteen minutes. A tenminute immersion period ninn'm isopmpmide'sathmted leather is heatedWlth f will, on the other hand, often be suflicient when the fattySolvent Solution 06 a P" fatty held- 40 acid solution is pre-heated toabout C. Since, for

This can be aeeomphshed i y convenient F but all practical purposes thisdifference is not deemed' to P h fi p 18 cnmed out by mp s the be toohighly significant, the reaction is preferably al- Jrated leather in asell- 0f the fatty aeld- The l lowed to occur at ordinary roomtemperatures.

ment of the saturated leather with the solvent solution As indicatedheretofore, the third step in our process If fatty acid results information, in F 9 F e involves washing the treated leather in a solvent,such Proofing "aluminum Salt of the fatty acld fivlthlh the as, anaromatic hydrocarbon, to remove any unreacted terstices of the leather.Isopropyl alcohol 1s also formed. ingredients present This step iscarried out at room The formation of the water-insoluble aluminum salt1n temperature f bl but, as was the case with the this unique mannergreatly enhanee$ the Teslstahce preceding steps in the process, it toocan be carried out leather to penetration by water and moisture. Inthenext 50 at elevated temperatures, that is, temperatures up to P, thefine-1 p of the Ph r the leather 1s Washed about 50 C., if desired. Thewashing operation can free of any unreacted aluminum ISOPI'OP and fattybe performed in any convenient manner but it is most acld present by m nof the use of a shltahle easily accomplished by immersing the treatedleather solvent. After w s g, the waterproofed leather 15 P in a vat ordrum of fresh solvent. Alternate methods mlfleq y at room temperaturefor accomplishing the desired result, however will be As mdle tedheretofore, the seeohd step 0f the Pl'ocess readily apparent to personsskilled in the art. Imcontem'p t the use Of a 015, W Ila-Sheen mersionof the treated leather in the solvent for not re to pfatty acld- BY welonger than about ten minutes, and generally for about mean that asolution of an aliphatic monocarboxylic acid, five minutes will besuflico either saturated, unsaturated or hydroxylated, which has 0Finally, "when the i gg i g g g zzgt fi a cimhon length of from about 12to about 24 leather is permitted to air dry. The waterproofed carbonatoms is employed. Thus, for example, soluleather ma be sub-actedthereafte a r to other conventi trons of soap-formlng fatty acids, suchas lauric acid, processingyor finisllling steps. anal myristic acid,palm-itic acid, stearic acid, behen-ic acid, It should be understoudthat th e se uenc d d a; gs 3 :5 or of 2 heretofore of treating theleather fir t with 5: :11- 0 are y or n e pm err minum iso propoxidesolution and then with the fatt y acld m z g tg gg ggg sggf of laumcacid 01cm solution represents only the preferred method for prac- Anyorganic solvent in which the fatty acid is soluble ficing our fh' Thissefluehc? is h critical insom; at s time, with 10 is: 2...: ii iil ltfifsza zrrltzrrss. use m eprecc mg stepo eprocesscan' u ire both inproducing the fatty acid solution employed i h Thus, for example, theleather to be waterproofed could second step and in the washingoperation of the third step. be saturated with the solvent solution ofthe fatty acid In the preferred practice of the invention, however,aroin the first step of the process and in the second step matichydrocarbon solvents, such as, benzene, toluene, the saturated leathercould be treated with the solvent solution of the aluminum isopropoxide.The various disclosures heretofore with respect to the practice of theinvention by preferred method are applicable equally with respect to thepractice of the invention by the alternate procedure. As in thepreferred method, treatment by the alternate procedure results in theimpregnation of the interstices of the leather with the desiredwaterproofing aluminum salt.

Many advantages accrue from the practice of our invention. First, by itsleathers which are highly resistant to penetration by water and-moisture are obtained. Moreover, the process is economical andcommercially feasible. It does not require the use of equipment notalready in use in leather tanneries, and its practice does notnecessitate a knowledge of special techniques. Furthermore, leathertreated as disclosed herein is protected indefinitely. This is incontrast to leather which, in the prior art, has been surface treatedwith fats, waxes and preformed aluminum soaps. Such treatment affordstemporary protection only. When the aluminum soap is formed in situ, bythe two stage process described herein, it impregnates the leather.Permanent protection is thus provided since the impregnant cannot beabraded or washed away. Moreover, the process is noteworthy in thatneither the air permeability nor the water-vapor permeability of theleather is adversely affected thereby. Finally, treatment by our processdoes not result in the discoloration or darkening of the leather. Thelatter feature will render the process invaluable for use in thewaterproofing of light, and particularly white, leathers.

For a fuller understanding of the nature and objects of this invention,reference may be had to the following examples which are given merely asfurther illustrations of the invention and are not to be construed in alimiting sense. All parts given in. the examples are parts by weightunless otherwise indicated.

Example I Samples of side leather were waterproofed by process of theinvention. The leather employed was chrome tanned, syntan retanned andfat-liquored.

A solution comprising benzene having dissolved therein 3.0% by weight ofaluminum isopropoxide was first prepared. This solution was divided intotwo parts. A sample of side leather designated, hereinafter as sample I,was immersed in one of the parts of the solution. It was retainedtherein for a period of about 30 minutes. The solution had a temperatureof about 27 C. An

other sample of the same/side leather, designated hereinafter as sampleIL/was immersed in the second part of the solution and {tamed thereinfor a period of about 15 minutes. The" solution used had a temperatureof about 27 C.

Each sample of leather was removed from the solution at the end of thedesignated time. Sample I was immediately immersed in a solutioncomprising 3.0% by weight of oleic acid in benzene and it was retainedtherein for a period of about 30 minutes. This solution had atemperature of about 27 C. Sample II was immediately immersed in a 3.0%by weight solution of oleic acid in benzene and retained therein for aperiod of about 15 minutes. This solution had a temperature of about 27C.

At the end of the designated period of time, each of the samples ofleather were removed from the oleic acid solution. Each was thereafterwashed free of unreacted materials by immersion in benzene for a periodof about minutes. Each sample was thereafter removed and allowed to dryat room temperature. Each of the dry samples were tested for staticwater absorption by the American Leather Chemists AssociationProvisional Method, April 1953 (Test Method E 30). Static waterabsorption is defined therein as the amount of water absorbed by leatherwhich is immersed withoutflexing in water for a specified period oftime. The test method contemplates two immersion periods in water,namely,

30 minutes and minutes. The method gives an adequate indication of thepercent of water absorbed by leather in the specified periods of time.The following are the results of the static water absorption tests.

The foregoing procedure was repeated in every detail except that where a3.0% by weight aluminum isopropoxide solution was employed originally, a5.0% by weight solution thereof was instead used, and where 3.0% byweight of oleic acid solution was originally used, a 5.0% by weight ofthe oleic acid solution was instead emplayed. The samples of leatherthus treated were tested for static water absorption in the same manneras were samples I and II. In the table which follows hereinafter, thedesignation sample III refers to the product corresponding to previoussample I. The designation sample IV refers to the product correspondingto the previously mentioned sample II. The result sof the static waterabsorption test were as follows:

Percent Water Absorption Immersion Period 30 minutes 120 minutes Theforegoing procedures were repeated in every detail once again exceptthat, in this instance, 10.0% by weight solutions of aluminumisopropoxide in benzene and 10.0% by weight solutions of oleic acid inbenzene were used instead of the 3.0% by weight and 5.0% by weightsolutions previously employed. These samples were tested for staticwater absorption in the same manner as were samples I to IV, inclusive.In the table which follows hereinafter, the designation sample V refersto a product corresponding to previously mentioned samples I and III.The designations, sample VI refers to a product corresponding to theprevious samples II and IV. The results of these tests were as follows:

Percent Water Absorption 30 minutes 120 minutes The foregoing resultsfurnish conclusive evidence that excellent waterproofing can be achievedwhen leather is treated by the process of our invention. However, inorder to demonstrate that the result obtained is attributable to areaction between the aluminum isopropoxide and oleic acid, in situ,rather than merely to the deposition of a coating of water-insolublefatty acid in or on the leather, the following experiments were carriedout. A solution of 3.0% by weight of oleic acid dissolved in benzene anda solution of 5.0% by weight of oleic acid dissolved in benzene wasfirst prepared. Into each of the two solutions a sample of chrometanned, syntan retanned and fat-liquored side leather was immersed. Inone case, the leather was allowed to stand in contact with the 3% oleicacid solution for 30 minutes. The leather thus treated will be referredto hereinafter as sample VII. The second sample of leather hereinafter,designated as Percent Water Absorption (Samples Treated With Fatty AcidOnly) Immersion Period. 30 minutes 120 minutes Sample v11 -Q no 116Sample VIII 95 97 Since it is well known in the art that the propertiesof aluminum isopropoxide are such, that it alone could not be used andwould not function as a waterproofing agent and since the foregoingresults demonstrate that oleic acid alone is ineffective, the results ofthe static water absorption tests reported herein conclusively provethat the present process provides a valuable method of waterproofinleather.

Anexamination of the leather after treatment by the method disclosedherein reveals that in each instance the sample was waterproofed withoutsacrificing the air and water vapor permeability thereof and withoutdarkening or discol'oring the leather.

Example 11 In this example the procedure of Example I was repeated inevery detail except that calfskin rather than side leather was employedin this example. The calfskin used was chrome tanned and syntan retannedbut it had not been fat-liquored prior to waterproofing.

Calfskin (sample I) was treated at a temperature of 27 C. by immersingit first in a 3.0% by weight solution of aluminum isopropoxide inbenzene for 30 minutes and thereafter in a 3.0% by weight solution ofoleic acid in benzene for 30 minutes. benzene for minutes and finallyair-dried.

Calfskin (sample II) was treated at a temperature of 27 C. by immersingit first in a 5.0% by weight solution of aluminum isopropoxide inbenzene for 30 minutes and thereafter in a 5.0% by weight solution ofoleic acid in benzene for 30 minutes. The leather sample was then washedin benzene for a period of about 5 minutes and finally air-dried.

Calfskin (sample III) was treated at a temperature of about 27 C. byimmersing it first in a 10.0% by weight solution of aluminumisopropoxide in benzene for 30 minutes and thereafter in a 10.0% byweight solution of oleic acid in benzene for 30 minutes. The leathersampic was then washed in benzene for about 5 minutes and finallyair-dried.

Calfskin (sample IV) was treated in the same manner as sample I exceptthat it was immersed in the benzene solutions of aluminum isopropoxideand oleic acid for 15 minutes rather than 30 minutes.

Calfskin (sample V) was treated in the same manner as sample II exceptthat it was immersed in the benzene solutions of aluminum isopropoxideand oleic acid for 15 minutes each rather than 30 minutes.

Calfskin (sample VI) was treated in the same manner as sample III exceptthat it was immersed in the benzene solutions of aluminum isopropoxideand oleic acid for 15 minutes each rather than 30 minutes.

Calfskin (sample VII) was treated in the same manner as sample I exceptthat the benzene solutions of aluminum isopropoxide and oleic acid wereheated to a temperature of 50"v C. priorto immersing the leather thereinand except that the leather was allowed to remain immersed in each ofthe solutions for 10 minutes rather than for 30 minutes.

The leather was then washed in Calfskin (sample VIII) was treated in thesame manner as sample II except that the solutionsof aluminumisopropoxide and oleic acid used were heated to a temperature of 503C.prior to immersing the leather therein and except that the leather wasallowed to remain immersed in each solution for 10 minutes rather than30 minutes.

Calfskin (sample IX) was treated in the same manner as sample III exceptthat the solutions'of aluminum isopropoxide and oleic acid were heatedto a temperature of 50 'C; prior to immersing the leather therein andexcept that the leather was allowed to remain immersed in each solutionfor 10 minutes rather than 30 minutes.

For comparative purposes the basic procedure employed in treating eachof samples I to III, inclusive, and VII through XI, inclusive, of thisexample was repeated in every detail except that the steps of immersingthe leather in the solution of aluminum isopropoxide and the step offinally washing the treated leather in benzene were omitted. In thetables which follow hereinafter the samples corresponding to samples I,II, III, VII, VIII and IX are designated as samples X, XI, XII, XIH, XIVand XV respectively.

Each of the dry samples were tested for static water absorption by theProvisional Method of the American Leather Chemists Association, April1953, referred to heretofore. The following are the results of thosetests:

Percent Water Percent Water Absorption (Samples Treated With Fatty AcidOnly) Immersion Period 30 minutes 120 minutes Sample X 110. 5 113 SampleXI. 107 108 Sample XII 116. 5 108 Sampl XIIL. 135 136 Sample XI 137 137Sample XV 1Q 142 These results demonstrate the extent to which leathertreated by our method was rendered water-repellant. It was furtherobserved that this result was accomplished without darkening ordiscoloring and without adversely affecting the air or waterpermeability of the leather.

Example III In this example, samples of chrome tanned side leather weretreated.

A solution of 3.0% by weight of aluminum isopropoxide was firstprepared. This was divided into three parts. A separate sample ofleather was immersed in each solution and retained therein for a periodof about 30 minutes.

The temperature of the solution used in each instance was After 30minutes each sample was removed from its fat-X t'y acid bath and washedfree of unreacted materials by immersion in benzene for about minutes.Each sample was removed thereafter and allowed'to dry at roomtemperature.

For comparative purposes, the procedureused in waterproofing each of thesamples I, II andlII'was repeated except that in each instance the stepsof immersing the leather in the aluminum isopropoxide solution and 'of'washing the leather in benzene were omitted. In the tables which followhereinafter, the comparative'samples which correspond to samples 1,11and HI have been designated at samples. IV, V and VI respectively. aEach of these six samples of treated leather were tested for staticwater absorption by the Provisional Method of American 'Leather ChemistsAssociation, April 1953', referred to in Example I. The results of thetests thus conducted were as follows:

Percent Water Absorption Immersion Period 30 minutes 120 minutes PercentWater sorption (Samples Treated Wlth Fatty Acid Only) Example IV In thisexample, chrome tanned, high grade sheepskin, a soft leather of the typeused in the glove and garment industries, was employed. The leather wasfat-liquored and air-dried prior to use.

A sample of this leather, hereinafter referred to as sample I, wasimmersed first in a solution of 3.0% by weight of aluminum isopropoxidein benzene and retained therein for 30 minutes. The solution used had atemperature of 27 C. After immersion in this solution, the leathersample was removed and it was immersed immediately in a solution of 3.0%by weight stearic acid in benzene and retained therein for a period of30 minutes. The stearic acid solution used had a temperature of 27 C. Atthe end of the designated period of time the sample was removed from thestearic acid solution, immersed in benzene and retained therein for 5minutes and thereafter air-dried.

The dynamic water resistance of the leather thus treated was tested bythe American Leather Chemists Association Provisional Method, April 1953(Test Method B 31). For comparative purposes, a sample ofnon-waterproofed sheepskin which was chrome tanned and fat-liquored wassubjected to the same test method. This non-waterproofed leather samplewill be referred to hereinafter as sample II. For further comparison,chrome tanned sheepskin, which after fat-liquoring and drying, waswaterproofed using chromium couples was also subjected to the 70 dynamicwater resistance test. This sample will be referred to as sample III.Finally, chrome tanned sheepskin which, after fat-liquoring and drying,had been waterproofed using chromium couples and which was further plewas alsotested for dynamic water absorption. This is sample IV.

The test for dynamic water absorption revealed that, of all the samplestested, sample I, that is, leather treated by the process of this.invention, was most resistant to the penetration of water. Initialtwaterpenetration of sample I occurred only after 7,500 cycles. The testproved sample IV to be secondbest, with water penetrating the leatheronly after 6,500 cycles, sample III was shown to be. thirdxbest, withwater penetrating the leather only after 5,500 cycles. In thecase ofsample II, water penetrated the leather almostinstantly.

: 'Ihe American Leather. Chemists Association Test for;

static water absorption was then carried out in connection withsamples Iand III. 'It was found that'sample III which was waterproofed using onlychromium couples took up as much as 107% water whereas sample I absorbedonly 32% in the same period of time.

The foregoing results conclusively demonstrate that 80-. periorwaterproofing of leather is provided by the process of the presentinvention. In addition, examination of leather which was subjected tothe method disclosed herein revealed that the desired water repellingproperties were achieved without darkening or discoloring of theleather. 4

Having described our invention what we claim as new and desire to secureby Letters Patent is:

l. A method of waterproofiing leather with an aluminum salt of analiphatic monocarboxylic acid having a carbon chain length of from about12 'to about 24 carbon atoms consisting essentially of impregnatingtanned leather with a solution consisting of an aromatic hydrocarbon andaluminum isopropoxide', and with a solution consisting of an aromatichydrocarbon and an aliphatic monocarboxylic acid having a carbon chainlength of from about 12 to about 24 carbon atoms and subsequentlywashing the leather thus treated with an aromatic hydrocarbon solvent.

2. Tanned leather produced by the process of claim 1 characterized byits water repellency, the permanency of its water repellency, and itsair permeability and water vapor permeability and further characterizedin that it is not discolored or darkened as a result of that process.

3. A method of waterproofing leather with an aluminum salt of analiphatic monocarboxylic acid having a carbon chain length of from about12 to about 24 carbon atoms consisting essentially of immersing tannedleather in a solution consisting of an aromatic hydrocarbon and fromabout 3.0% to about 10.0% by weight of aluminum isopropoxide for aperiod of time sufiicient to saturate said leather with said solution,immersing said leather in a solution consisting of an aromatichydrocarbon and'from about 3.0% to about 10.0% by weight of an aliphaticmonocarboxylic acid having a carbon chain length of from about 12 toabout 24 carbon atoms and subsequently washing the leather thus treatedby immersing it in an aromatic hydrocarbon solvent.

4. A method of waterproofing leather with an aluminum salt of analiphatic monocarboxylic acid having a carbon chain length of from about12 to about 24 carbon 0 atoms consisting essentially of immersing tannedleather in a solution consisting of an aromatic hydrocarbon and fromabout 3.0% to about 10.0% by weight of an aliphatic monocarboxylie acidhaving a carbon chain length of from about 12 to about 24 carbon atomsfor a period of time sutricient to saturate said leather with saidsolution, immersing said leather in a solution consisting of an aromatichydrocarbon and aluminum isopropoxide and subsequently washing theleather thus treated byimmersing it in an aromatic hydrocarbon solvent.

5. A method of waterproofing leather with an aluminum salt of analiphatic monocarboxylic acid having a carbon chain length of from about12 to about 24 carbon atoms consisting essentially of immersing tannedleather in a solution consisting of about 3.0% to about 10.0% bysubjected to the treatmentgiven to sample I of this examweight ofaluminum isopropox-ide and an aromatic hydro- 1 1 arbon solvent selectedfrom the group consisting of ben- :ene, toluene and xylene for a periodof time suflicient to aturate said leather with said solution, immersingsaid eather in a solution consisting of 3.0% to about 10.071: y weightof an aliphatic monocarboxylic acid having a :arbon chain length of fromabout 12 to about 24 carbon ltoms in an aromatic solvent selected fromthe group conisting of benzene, toluene and xylene and subsequentlyvashing the leather. thus treated by immersing it in an tromatichydrocarbon solvent selected from the group mnsisting of benzene,tolueneand xylene.

6. A method of water-proofing leather with an alumilum salt of a fattyacid selected fromthe group consisting f lauric acid, stearic acid andoleic acid consisting essenially of immersing tanned leather in asolution consisting )f from about 3.0% to about 10.0% by weight of alu--ninum isopropoxide and the remainder being an aromatic lydrocarbonselected from the group consisting of benene, toluene and xylene for aperiod of time suflicient to aturate said leather with said solution,immersing said eather in a solution consisting of from about 3.0% tolbOllt 10.0% by weight of an aliphatic monocarboxylic lcid selected fromthe group consisting of lauric acid, itearic acid and oleic acid and theremainder being an I carboxylic acid employed is lauric acid.

8. The process of claim 6 wherein the aliphatic monocatboxylic acidemployed is stearic acid. 7

9. The process of claim 6 wherein the aliphatic monocarboxylic acidemployed is'oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS1,242,327 Cuthbertson Oct. 9, 1917 2,182,045 Bell Dec. 5, 1939 2,323,387Edelstein July 6, 1943 2,603,576 Cook et al. July 16, 1952 2,670,303Mailander Feb. 23, 1954 FOREIGN PATENTS 609,002 Great Britain Sept. 23,1948 767,585 Great gritain Feb. 6, 1957

1. A METHOD OF WATERPROOFING LEATHER WITH AN ALUMINUM SALT OF ANALIPHATIC MONOCARBOXYLIC ACID HAVING A CARBON CHAIN LENGTH OF FROM ABOUT12 TO ABOUT 24 CARBON ATOMS CONSISTING ESSENTIALLY OF IMPREGNATINGTANNED LEATHER WITH A SOLUTION CONSISTING OF AN AROAMTIC HYDROCARBON ANDALUMINUM ISOPROPOXIDE, AND WITH A SOLUTION CONSISTING OF AN AROMATICHYDROCARBON AND AN ALIPHATIC MONOCARBOXYLIC ACID HAVING A CARBON CHAINLENGTH OF FROM ABOUT 12 TO 24 CARBON ATOMS AND SUBSEQUENTLY WASHING THELEATHER THUS TREATED WIHT AN AROMATIC HYDROCARBON SOLVENT.